I suspect this is WAD. They can still blow up in your face. If useless I just scrap them. Sometimes I just scrap them anyway. Occassionally they can be left to clear out any remaining space creatures and then scrapped. The easy way to find out if they mine anything is zooming out to the system screen and then clicking on the asteroid. Otherwise it can be hard to tell and you have to wait to see what, if anything, they will produce.

Are you sure it was a mine? I have seen abandoned starbases using mine pictures and so on... I am not sure that that the random stuff is constrained by the parameters of the rest of the game...

Has happened several times where it turned out to be a mine. I always check the components to see if it's worth keeping. And I check both the cargo bays and the rock it sits on to see if any mining is occurring.

Re: ice asteroids, I've never seen one of these with anything to mine - only metal asteroids. Do I need to be checking closer?

Re: ice asteroids, I've never seen one of these with anything to mine - only metal asteroids. Do I need to be checking closer?

About ice asteroids I am not sure, barren rock asteroids seem to be similar, though. Those rarely have anything mineable, but it still happens occasionally. I suspect ice asteroids may be the same. Since finding the needle in the haystack is difficult, it is best left o automated constructors to make use of these resources., if they choose so.

Regarding the original issue:

It is very common for abandoned mining or gas mining stations to appear where there is no mineable resource or on the wrong kind of planet/moon/asteroid, so the extractors do not work. The main purpose of these objects is probably to provide hints regarding the story line with their navigational directions in some data core. After that, they're just a drain on the economy, as you have to pay maintenance, and should be scrapped. Since I typically find them in some backwater, far from my colonies, scrapping them looks like the thing to do, even in the rare case that the mining equipment has something to work on.

The same treatment is recommended for the occasional abandoned starbase with its space yards. Ships may go for repairs there instead to a planetary space port. Or worse, construction from the civilian sector or ships issued via the build orders screen may land here. These star bases are usually slow to build anything, in part because they seem to be very low priority in receiving supply shipments. This is from experience in old versions of the game. There were some notes regarding this in recent patches, so maybe it isn't an issue any more.

Ice asteroids can have minable resources. The only thing I check manually for is gold nuggets and their ilk. Checking show asteroids in the expansion planner lets you assign constructors manually without having to click on every asteroid. This list can get very long later in the game.